Por/para ... and others ... and there are similar difficulties for Spanish speakers learning English. (And I would assume with other languages as well....)

In thinking about this, I have come to the conclusion that the difficulty lies where there is ONE word in a language that can be translated as TWO different words (with different uses) in the other language.

Some examples:

Spanish >>> English
ser/estar = to be
por/para = for
saber/conocer = to know

English >>> Spanish
get = muchas palabras

I know there are more, but these are the ones that frequently come to mind......

to remain, to be left, to meet .......... I can sort of follow those ... but when it is used as an auxiliary verb with other verbs...... I am frequently surprised by the uses that native speakers find for "quedar"..............